The Green River or Groen River () is a river in the Northern Cape province of South Africa. It originates in the Kamiesberge range and has a catchment area of about 4500 km<sup>2</sup>. The river mouth is located about 120 km NNW of Strandfontein in the Namaqua National Park area by the Green River Mouth Lighthouse.
There is diamond exploration in the Green River Valley.